Update nginx-unit and allow custom nginx-unit.json config

[tagur87]

Desired Behavior

We are running into an issue with nginx-unit used in the netbox-docker image where we are getting an HTTP 431 due to the large header size of our k8s ingress.

Nginx-unit team is working on a fix(nginx/unit#771), but we will need this project to be updated once this is released.

We will also need to be able to add the following config entries to the nginx-unit.json file

"settings": {
    "http": {
        "large_header_buffer_size": 16384
    }
},

Contrast to Current Behavior

There does not appear to be a way to add a custom nginx-unit.json config file through an environment variable or similar. We would prefer this be an option so we don't have to roll our own image.

Required Changes

Add an option to allow a custom nginx-unit config file to be provided to a consumer of the docker image.

Discussion: Benefits and Drawbacks

This would allow others to specify unique configurations for nginx-unit in their projects.

[cimnine]

Isn't it possible to mount a custom nginx-unit config file where our default file is?

With an ENV variable you'd have to either build your image as well, or mount a config file. I believe it's possible to skip the ENV variable part and already mount a custom config file to the proper location.

[tagur87]

I was initially thinking of something like how it's done in https://github.com/netbox-community/netbox-docker/blob/release/configuration/configuration.py but since unit is external to netbox that doesn't make much sense.

I agree that we can just override it in our deployment with a custom file.

Will close this for now and reopen when the new version of nginx-unit is released to request an update.